1. Field of the Invention
The present invention relates to an image processing apparatus, such as a personal computer, which performs compression coding of image data according to JPEG2000 algorithm, and also relates to an image processing method which performs compression coding of image data according to JPEG2000 algorithm, and a storage medium storing a program embodied therein for causing a computer to execute the image processing method.
2. Description of the Related Art
With the recent development of computer networking, the spreading speed of Internet systems including personal computers is actually accelerated.
In such situations, the server, which distributes contents to the servers as the distribution source, handles various images when creating the contents. Namely, the various images handled by the server include a natural image like a photograph which is taken with a digital camera or inputted from a scanner, a computer graphics image (CG image) which is artificially created by a computer, a bi-level image like a usual document, a palletized text-picture image (or palletized color image) expressed in the pallet color according to the pallet color method, and a monochrome image. There may also be many cases in which these various images are complexly included in a document.
For example, in a case of a CG image, when compared with a natural image like a photograph image, it has the characteristics that the pixels of the same color may be continuous and the colors between the neighboring pixels are different extremely. Moreover, as for the color images, there is the characteristic that a natural image with each color of RGB for 8 bits, being inputted from a digital camera, and a palletized text-picture image, using the pallet color have a different composition of the image data.
On the other hand, it is essential that the server handles various images and carries out the compression coding and storing of the images, in order to make it possible to save the memory space and lessen the data capacity enabling the high-speed transmission of the image data during the contents distribution.
Conventionally, it is known that one of the compression coding of bi-level images and the compression coding of multi-level images is selected by switching when performing the compression coding processing mentioned above.
For example, Japanese Patent No. 2814970 (which corresponds to Japanese Laid-Open Patent Application No. 09-150556) discloses an image processing method in which two different encoders are provided, an image is partially compressed by using one of the encoders, the type of the image is determined from the compression ratio of the compressed image, and the final compression method is selected according to the image type.
Moreover, the image compression technology of JPEG2000 algorithm attracts the attention as the technology of high compressibility image encoding/decoding in which the encoded image can be restored with high quality of image.
Although the image processing method of Japanese Patent No. 2814970 can carry out the image compression processing selectively depending on the image type (or on whether the image is a bi-level image or a multi-level image), the plural encoders for compression encoding of the different image types must be provided. Such image compression processing is not efficient, and the composition of the whole image processing apparatus will become complicated and the cost will be raised because of the use of the plural encoders. Moreover, the image types for which the compression coding is possible will be limited to the bi-level image or the multi-level image.
Moreover, when JPEG2000 algorithm is used, some processings for efficient compression encoding are included and it is basically efficient and high compressibility can be attained. However, such processings are not necessarily effective for the characteristics of some image types. On the contrary, there is the case in which the encoding efficiency becomes poor because of the use of such processings.